Pompeii oven in South Africa
I've posted a few messages/photos in the yahoo group about my oven. It seems that this forum has more space for photos so I decided to post some photos and comments here with the hope that it may help someone else like other people's postings and photos have helped me.
These first photos are of the foundation slab.
Building the base
Here are a few photos of the building of the cinder block base.
The blocks I found were not the same size as the ones I saw in other people's postings, but they seem to have worked ok.
I built an "Island Hearth" (or is it "Floating Hearth") and was scared that the vermiculite cement mix will not be strong enough to support the oven, so I placed all the steel I could find accross the base to support the hearth and oven.
We were doing some home renovations and I had some left over "Think Pink" ceiling insulation which I placed on top of some old ceiling boards, before I cast the insulating vermiculite concrete. However I do not think that the Think Pink will add any insulation value as it was totally compressed by the concrete:(
I have not seen a photo of an Island Hearth, but using the descriptions in the yahoo forum I placed a wooden frame onto the initial layer of vermiculite concrete. I poured normal concrete into the inside of the frame with vermiculite concrete on the outside.
It turns out that I should have given much more thought on how to remove this wooden frame, but more on this later:)
The cinder blocks in these photos were used to keep the top of the frame level.
A week later I marked the center lines of the hearth so I could lay my bricks starting from the center.
I also made two polystyrene vanes for the building of the dome. I planned to build a 110cm (about 43") oven, so I drew a semicircle (with a 55cm radius) on each piece of polystyrene and then freehand adjusted the curves to give a slightly "flatter" looking dome. I kept the height at 55 cm, but "fattened" the curve a bit on the sides. I cut a center slot halfway from the top of one vane and halfway from the bottom of the other and inserted the two slots into each other to form the template as seen on the photos.
My bricks were not very evenly shaped, and sometimes not even very square at the corners, but I managed to find the best ones to use in the oven floor.
I drew a circle on the floor bricks and placed my first layer of dome bricks with their insides on the circle, as per the Pompeii oven plans. I adjusted the bricks a bit so that I did not have to cut a brick in this first layer.
For the second layer I used my polystyrene template and some of my wife's pins she uses on the washing line (I think they are called clothe pins) to get the bricks at the correct angle. This was a lot of effort and for the subsequent layers I simply placed some mortar at an angle on the previous layer and adjusted each brick to sit at the angle of the polystyrene vane at that height.
Because my polystyrene template only had four "legs" I had to keep turning it so that one of the vanes were next to the brick I was busy with. This also meant that my bricks did not actually rest on the polystyrene.
I was a bit nervous at first, but once a layer's key stone was cut (not very accurately, i might add) the bricks stayed in place nicely.
Completing the dome
The fire bricks I found were about 23 x 11.5 x 8 cm which is "thicker" than the ones recommended. This meant that my dome went up fairly quickly, but also that it was difficult to keep the gaps small.
A friend arranged some stainless steel for me which I used to span the opening with. I was also a bit nervous of doing this (getting the heights correct, etc) but it was easier than I anticipated:)
By the time I got to the last three, or so, rows it was difficult to keep the bricks from slipping down before the key stone was inserted. I had some thickish wire available so I rolled this into loops which I placed on top of the polystyrene and I actually rested the bricks on the wire. By now I was really tired so I did not take any photos--sorry.
At this time South Africa started playing rugby against New Zealand, and I rushed to finish (always a bad idea). This meant that I simply cut the last bricks into thirds and did not fill all the gaps on the inside of the dome properly. So if you look at the top of the oven from the inside, there are some "air gaps" between the bricks. However at the top the gaps are filled and the dome seems strong enough.
In retrospect it would have been better to place some newspaper on top of the wire befora laying the bricks. This would have stopped the mortar from falling out at the bottom and creating the gaps.
The next day I "buttered" the dome with 10mm of mortar and covered it with plastic for a week to cure.
Removing the wood frame
The oven floor fitted nicely on the island hearth, so untill now I did not have to worry about removing the wooden frame around it.
Twood of the frame was nicely wet and did not budge at all. In the end I drilled some holes in the wood and used a hammer and a chisel to laboriously cut a slot down the center of each piece before they could be removed.
The gaps left by the wood between the hearth and the insulating vermiculite concrete was filled with vermiculite concrete.
I extended the floor to the front and built a brick chimney. I could not find clay flue liners in South Africa and the alternatives were very expensive, so I built it with brick only.
I again spanned the opening with stainless steel, but plan to still build an arch to hide the steel that you can see in the photos.
Later on I added three more rows ob bricks to increase the height of the chimney. It was drawing well enough but I thought that adding some height will make it look a bit better (hoping to draw attention a way from my poor masonry skills:)
Fire and Pizza
Last week I made a series fires which I increased in size every day. By the third day some cracks appeared which I filled with fire cement, even though they were not very big.
By Sunday the top of the dome started to burn white and we had our first pizza using bread dough we bought at the supermarket (too lazy to make our own). Afterwards I placed the left over dough in the oven and closed the opening. Hopefully this is the first of many pizza and bread bakings:)
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